Child cardboard cutouts outside parliament

Cardboard cut-outs of children have been placed outside Parliament House as humanitarian groups call on Australia to release children from immigration detention on Nauru.

Save the Children and Amnesty are ramping-up pressure on the Turnbull government ahead of two United Nations' summits on refugees and migrants in New York next week.

They say Australia must immediately resettle about 250 children they claim are on Nauru or at risk of being sent back there, and drastically increase its humanitarian refugee intake.

"These children can't be here. We're bringing their image right in front of politicians so they can't ignore them anymore," Save the Children's Tim Norton told reporters in Canberra on Wednesday.

Amnesty Australia says nothing Prime Minister Malcolm Turnbull says or does in New York next week will be able to hide the truth of what's going on on Manus Island and Nauru.

Thousands of leaked incident reports outlining abuse and self-harm on the Nauru were leaked in August.

More than half related to children.

Save the Children has also released a poll of more than 1000 Australians, showing about three-quarters want the government to accept New Zealand's offer to resettle refugees.

More than 90 per cent also support reuniting separated refugee families.